1. Field of the Invention
This invention relates to the field of pipelines and the filtration of products that flow therethrough.
2. Description of Related Art
Pipelines can transport any number of liquid or gaseous products. Because of the inherent nature of the material from which pipelines are constructed and the nature of the products that they carry, the internal surfaces of pipelines tend to become corroded over time, producing rust, sediment and the like. In addition, pipelines may contain construction debris, such as welding rods, rags, and sand, which is often present immediately after construction of a pipeline. Finally, the inside surfaces of pipelines may also become coated with various deposits, which accrue as a result of ordinary pipeline use.
The types of materials deposited on the inside surface of a pipeline usually depend on the type of pipeline and the product being conveyed by the pipeline. Typical accumulations include pipeline rouge, rust, mill scale, sediment, and materials attributable to specific operations, including paraffin deposits, sludges, and the like.
If allowed to accumulate, the corrosion byproducts and deposits will increase the possibility of pipeline leaks and/or rupture. The accumulation of corrosion byproducts and deposits will also eventually hinder the ability to transport product through the pipeline at optimum flow rates and will degrade the quality of the transported product. More importantly, the buildup of pipeline rouge, deposits, particulate matter, impurities, and the like may present a hazardous situation if left unaddressed, because such accumulations may reduce the overall surface area for a given cross-section of pipe, thereby increasing the pressure associated with a particular pipe section. If the pressure exceeds the design threshold, then the possibility of a pipeline rupture and/or explosion is imminent.
The aforementioned hazards are especially troublesome for owners or operators of pipelines that are used to transport gaseous products, which are often highly flammable. Gaseous products are commonly compressed (at compressor stations) during transit in order to move the product efficiently and to increase the volume a pipeline can transport. Thus, pipelines capable of withstanding high pressures are typically used in order to minimize pressure losses over long distances. High pressure pipelines are usually capable of conveying gaseous products at pressures of 600 psi or higher. Typical products that may be carried by high pressure gas pipelines include, without limitation, oxygen gas, methanol, propylene, polyethylene, methane, polypropylene, ethylene, hydrogen gas, and natural gas.
In the past, the problem of sediment and deposit buildup in pipelines has been addressed by isolating a targeted section of pipe and forcing a spherical or cylindrical object (a/ka/ a pipeline “pig”) through the line under pressure to remove the debris. A pig typically has wire bristles or a similarly abrasive surface that will contact the inner surface of the pipeline and scrape away any accumulations or loose sediment, which will be pushed along in front of the pig in the form of particulate matter as it makes its way through a given section of pipe. This process sometimes requires that the isolated section of line be taken out of service, which may have the effect of interrupting product flow over a long distance. Because high pressure gas pipelines optimally carry approximately 2,000 barrels/day (bbl/day), the cost of shutting down such a line can be very costly. An additional consequence of shutting down a high pressure pipeline is that any product located within the isolated section of line must be either disposed of by venting portions of the product to the atmosphere, or by routing it to another section of pipe. Both of these options require the wasting of precious resources. The same is true when isolating sections of a liquid pipeline.
In order to avoid the expense associated with taking a high pressure gas pipeline out of service, owners and operators of high pressure gas lines have long sought a means for removing sediment and accumulations from pipelines in a manner that avoids the need to take the line out of service. The need for such a device has also been driven more recently by various regulations that require pipeline owners or operators to perform pipeline integrity inspections and maintenance every few years. See, e.g., Department of Transportation (Office of Pipeline Safety) regulations at 40 C.F.R. Part 195.
A number of inventions have been developed that relate to the filtration of products in pipelines. For example, known prior art includes U.S. Pat. Nos. 6,328,812, 6,063,151, 5,775,442, 5,514,194, 5,055,180, 4,836,017, 4,209,311, 4,095,965, 3,778,799, 3,665,966, 3,546,926, 3,488,168, 2,937,503, 2,915,422, 2,767,138, and 2,252,959; and U.S. Pat. Pub. Nos. US 2003/0116500, 2003/0015481, and 2002/0079248. However, each of these references and applications fails to address each of the aforementioned problems.
What is needed is an improved filter assembly that will allow the owner, operator, or contractor to filter products transported by pipeline in order to remove any debris, sediment, or other impurities from the product itself. What is further needed is an improved filter assembly that will allow the filtering of product to occur without requiring the owner or operator to take a particular section of product line out of service for a significant period of time. What is further needed is an improved filter assembly for use in connection with high pressure gas pipelines.